Electron discharge device



1950 s. o. EKSTRAND ET AL 2,494,593

ELECTRON DISCHARGE DEVICE Filed Dec. 24, 1946 3 sheets-sheet 1 FIG.

. S. 0. EKSTRAND INVENTORS C. MAGGS By I! L. RONC/ A T TORNEV Jan. 17,,1950 s. o. EKSTRAND ET A]. 2,494,693

ELECTRON DISCHARGE DEVICE Filed Dec. 24, 1946 s Sheets-Sheet 2 C mwu 5 0KAR EML QCV. S

INVENTORS.

FIG. 2

Jan. 17, 1950 s. o. EKSTRAND ET AL ELECTRON DISCHARGE DEVICE 3Sheets-Sheet 3 Filed Dec. 24, 1946 s. 0. EKSTRA/VD /NVEN7OR5. c. macsIKL. RO/VC/ 9 W ATTORNEY Patented Jan. 17, 1950 ELECTRON DISCHARGEDEVICE Store *0. Ekstrand, Bergenfleld, N. 1]., and flharlesMazgsamlWictorL Ronci, New York, N. Y., asnignorsdo Sell TelephoneLaboratories, Incormutated, New York, N. Y., a corporation of .New

York

Application December 24, 1946,, Serial No. 718,170

.16 fllaims. (Cl. 1259*?21-50 invention relates to electron dischargedevices and more particularly to themnaliy tunable reflex oscillators of:thel-cavity-resonator type.

The performance .of reflex oscillators, as is known, ils rathercritically dependent upon the physical relation *of ithe constituentelectrodes and, -particularly upon the relation of the .elec trodes atthe ihoundaries. :01 the operating gap, and of the repeller electrodewith respect FIO this gap. In such devices intended :for operation atextremely high fretoierni-ies, for :example frequencies corresponding towavelengths of the orderiof a :few centimeteraor less, necessarily theelectrodes are small and adlosely spaced. Satisfactory operationrequires not only that the electrode spacings he small and conform to:prescribed values :but also that the electrodes the aligned with .ahigh degree of accuracy.

The realization of the requisite electrode spacings andalignmentiitselfinvolvesserious prob lems .of construction. Themaintenance of the desired relations during operation of the device iscomplicated by thermal effects due :tofthe heat generated at evenmoderate outputs and the small sizes of :the electrodes. Thermal effectsare of considerable :moment also when thermaltuning of the oscillator"utilized ior, iinasmuch as such tuning iis effected :hycontrol-of thetemperature of one ror'more elements, iit-Iis eminently desirable fromit-he sstandpoint of stable operation that it. abe independent of heatvariations in the resonator "system i. of the oscillator.

One object of this invention is to facilitate the construction :ofreflex oscillators :and more particularly of such oscillators of thethermally tunable l-type and suitable for operation :at .exceedinglyhigh frequencies.

iMore specifically, loneaohjectiof this invention is to expedite :the:realization of close electrode spacings and accurate alignmentrofftheelectrodes put-section associated with the cavity resonator and anelectronic thermal tuner element :for controllahly adjusting theresonant frequency of the oscillaterelement.

In accordance with one feature of this invention, {the internalstructure :of the device .is composed of a plurality of subassemblies,the cons'tituentielements-of each of which are accurately mounted inprescribed relation :to one another, and the several assemblies arefabricated into a unit bodil iinsertable into the enclosing vessel. Moreparticularly, onesubassembly, about which the others are built,comprises a lioundation member or plate having an opening therein. andgrids at opposite ends .of the opening, one of the grids Eheing mountedby a flexible diaphragm, and the two grids, atogether with the diaphragmand :the eboundary wall of the opening defining a cavity resonator. Theplate is provided with a cut-out portion :or slot extending fromtheresonator. 'illheot-her suhassemblies are a wave guide and choke\un'it, one end of which is fitted into the cut-out portion or slot :inthe foundation member, an electron .gun assembly mounted from thedoundation :member, .a ltI'lOde tuner unit also mounted firom thefoundation membenand ,a repeller electrode :unit in which :the repellerelectrode is accurately aligned with the resonator grids by a sleeveextending-from :the diaphragm.

In accordance with another feature of this invention, the unitaryinternal assembly includes a relatively massive member of good heatcon-, ductivity, which :is affixed to the foundation member and in the[completed device is secured 35 to ime enclosing vessel and constitutesthe sole support-for *the unitary assembly. Additionally, this massivemember assures rapid dissipation of the heat'generated during theoperation of the device whereby the resonator is maintained at :a safeoperating temperature. and distortion of the elements thereof isprevented even at relatively high power outputs.

In accordance with a further feature of this invention, :means areprovided for effectively 5 segregatin the tuner :unit thermally from thecavity resonator assembly, whereby'the .eiiect of resonator"temperatures upon the tuner .is :minimized. "In :one {specific,construction, this means comprises a. member :of :high :heatconductivity coupled to the 'Ifoundation member and the re pellerelectrodeastructureiand defining a thermal shunt between the resonatorand the lumer.

fllhe iinvontion and the above-noted .and other features thereof willaloe understood more clearly typeireflex oscillatorieleinent, amavesguideiout and'afullydrom thegiollowing\detailedldescription withreference to the accompanying drawing in which:

Fig. 1 isan elevational view in section and to a greatly enlarged scaleof an electron discharge device illustrative of one embodiment of thisinvention;

Fig. 2 is an elevational view, partly in section, of the unitary mountassembly included in the device shown in Fig. 1;

Fig. 3 is a fragmentary detail view, partly in section, along plane 3-3of Fig. 1 of the cooling block and cavity resonator support included inthe device illustrated in Fig. l;

Figs. 4 and 5 are perspective views of the tuner unit assembly, theformer showing the assembly with the cathode and control grid unitremoved and the latter showing the structure with the repeller electroderemoved and being partly broken away to show details of the cathode andcontrol grid unit;

Fig. 6 is a plan view illustrating the manner in which one of the gridsof the radio frequency or cavity resonator unit may be fabricated;

Fig. '7 is a face view of one of the grids of the radio frequency unit;

Fig. 8 is a view in section taken along :plane 88 of Fig. 7; and.

Fig. 9 is an enlarged cross-sectional view of a subassembly included inthe device shown in Fig. 1.

Referring now to the drawing, the electron discharge device thereinillustrated is a thermally tunable reflex-oscillator especially suitablefor operation at frequencies corresponding to wavelengths of the orderof one or a few centimeters. It comprises, generally, a highly evacuatedenclosing vessel and a mount fabricated of several subassemblies unitedinto an integral structure which is insertable into the vessel as a unitand supported from an inner wall thereof.

The enclosing vessel, which advantageously is of metal, comprises acylindrical body portion Ill having flanges I I and I2 at opposite endsthereof, a dished base or header portion I3 hermetically sealed to thebase flange H and an inverted cup-shaped portion I4 hermetically sealedto, the flange I2. The cup-shaped portion M is provided with a centralaperture in its base in which a window i5 highly transparent toelectromagnetic waves is sealed.

Mounted within the enclosing vessel is a unitary assembly comprising aradio frequency unit including a reflex oscillator of the cavitresonator type and a wave guide output line or section for theoscillator, and including also a triode unit for tuning the cavityresonator. The components of this unitary assembly are built around arectangular plate I6 of a metal, such as silverplated steel, of highheat conductivity. The plate I6 extends into and is fixed in a slot in arelatively massive cooling block I8, also of a metal, such as silverplated steel, having high heat conductivity, which is secured, as bybrazing, tol the body portion II) of the enclosing vessel andconstitutes the support for the unitary assembly in the completeddevice. As shown in Figs. 2 and 3, the cooling block I8 is provided withrecesses I9 for receiving pellets I9A of brazing material. The plate Itand block I8 are coupled tothe base I3 by a pair of flexible metallicmembers Il, the function of which will appear presently.

The plate I6 is provided with a circular opening 20, defining a part ofa cavity resonator, and with a slot or cut-out portion 2I extending fromone edge thereof and having a restricted rec- 4 tangular portion 22opening into the opening 20, the slot defining a guide for receiving arectangular wave guide output section for the cavity resonator. Afiixedto one face of the plate It is a circular, metallic frame or support 23having a frusto-conicalvportion 24 extending into the opening 20,the-frusto-conical portion 24 mounting a dished or concavo-convex grid25 composed, advantageously, of wire mesh. Aflixed to the other face ofthe plate I6 is a retaining ring 26 which clamps an annular metallicdiaphragm 21, for example of Kovarjto the face. The construction isshown most clearly in Fig. 9. The diaphragm 21 is circularly andconcentrically corrugated and mounts an annular metallic support orframe 28 which carries a dished or concave- ,convex grid 29,advantageously composed of fine parallel wires.

- The grids 25 and 29, frusto-conical support 24, diaphragm 2i and thecircular wall of the opening 2i! in the-plate I6 bound acavity resonatorwhich is tunable by fiexure of, the diaphragm 21 and from which powermay be taken by way of the restricted portion 22-of the slot or cut-outportion 2I in the plate I6 and a wave guide 30.

The Wave guide 30 is formed of sheet metal, is of rectangular sectionthroughout and tapers from the cavity resonator toward the window I5,thereby to provide a uniform impedance along its length. As shown inFigs. 1 and 2, the guide fits in the slot or cut-out portion, 2I in theplate I6 and at its inner end has portions 3| overlying and affixed, asby welding, to the grid frame or support 23 and the retaining ring 26.

At its upper end, the wave guide is secured to an inverted, cup-shapedmetallic member 32'having an encircling flange 33- to provide a chokejoint adjacent the vessel portion I4, thereby to minimize loss-ofelectromagnetic energy propagated through the guide-and window I5. Themember 32 is secured to a cylindrical support or mount 34 having aflange 35 which is provided with intgeral fingers or-tabs 36. aflixed,as by welding, to the plate I 6.

.Cooperatively associated with the cavity resonator are an electron gunand a repeller electrode to constitute a reflex oscillator therewith.The electron gun comprises a metallic cathode member having acylindrical body portion 31 and a dished end portion 38, the concaveface of which has a coating 39 of electron emissive material thereon.-Disposed within the cathode member is a heater element 40, for examplea double helical filament coated with an insulatin material. Thecathode'member is supported from a focussing electrode having a centralcylindrical portion 4! and an annular flange 42, by a plurality, forexample three, of equally spaced wires or struts 43 welded to the flange42 and to the cathode member. The focusslng electrode is secured to aninsulating, e. g. mica, disc 44 by bent-over tabs 45 struck from theflange 42. The disc 44 is locked against an internal shoulder in adished-mounting member 46, by a locking band or collar 41, the mountingmember 46 being secured, as by brazingto the flange 23 of the supportfor the grid 25. The gun comprises a concaV0-00nvex accelerating andfocussing grid '60 carried by the base of the mounting member 46.

The repeller electrode comprises a cylindrical head portion 48 having adie punched concave face 49, and a shank portion 50 which is fitted inan insulating, e. g. mica, disc 5|, the latter being held against thehead portion 48 by a locking sleeve 52 welded upon. the shank. The micadisc 5| is fittedtightly within a metallic sleeve 53 which, as shownclearly in Fig. 9, abuts and is afilxed to the diaphragm 21. The sleeve53 is spaced from the head portion 48 of the repeller electrode and isfitted within and welded to a rigid, cylindrical drive member 54 havingan end flange 55 and an intermediate external collar or flange 56.

A U-shaped metallic bracket 5! is secured to the flange 55 and mounts aninsulating, e. g. mica, plate or strip 58 against which a thin,flexible, metallic strap 59 is locked by a metallic eyelet i affixed tothe shank 50. The strap 59, together with a conductor 6| sealed to aneyelet 62 on the base lit by a vitreous head 63, constitutes the lead-inconnection to the repeller electrode. It will be noted from theconstruction that this elec trode is insulated from the cavity resonatordefining members and, hence, may be operated at a potential differentfrom that of these elements.

The assembly comprising the repeller electrode 48, sleeve 53 and drivemember 54, which is coupled to the diaphragm 21 by virtue of theattachment of the sleeve and diaphragm to one another, is bodily movableaxially, whereby the diaphragm may be flexed to alter the configurationof the cavity resonator and, thus, to tune it. Such movement of thisassembly to tune the resonator is effected by an electronic tuner unitof such construction that very fine tuning may be obtained.

, The tuner Lmit, details of which are shown most clearly in Figs. 1, 4and 5, is carried by a metallic support aflixed to one end of the plateI and having outer arms 84 and an intermediate arm 65. It comprises apair of metallic struts 5t and El, advantageously of the same material,for example stainless steel, which are secured at one end to theintermediate arm 65 and at the other end to the collar or flange 56 onthe drive member 54. As shown clearly in Figs. 1 and 4, both struts areprovided with a longitudinal flute, the strut 66 extends substantiallynormal to the arm 55 and the other strut G'l is inclined relative to thefirst. It is apparent that if one or both of the struts are heated,because of the relative disposition and expansion of the struts, theends of the struts secured to the flange or collar 50, and, hence, theunitary assembly including the repeller electrode, will be displaced inthe direction substantially parallel to the longitudinal axis of therepeller electrode. The direction and amplitude of displacement, i. e.,to the left or to the right in Fig. 1, as the temperature of the strutschanges will be determined, of course, by the sign and magnitude,respectively, of the tem perature change. Such temperature changes areaccurately controllable in both sign and magnitude, by utilizing thestrut 66 as the anode of an electronic unit and controllin the electroncurrent to this anode.

The electronic unit comprises a pair of insulating, e. g. mica, platesor spacers 68 which are supported by a metallic frame or housing 59having flanges l'i affixed to the support arms 64. Mounted by the platesor spacers in alignment with the strut 66 are a cathode 12 ofrectangular cross-section and heatable to emission temperature by aninsulated, folded heater filament l3, and a rectangular grid 14 carriedby support rods or wires l5. The potential of the grid is appropriatelyvaried to control the electron current to, and, hence, the temperatureof, the strut anode 66, thereby to tune the cavity resonator to thedesired frequency.

A thin, flexible strip 16 of high thermal conductivity material, such ascopper, is connected at one end to the unitary assembly including therepeller electrode, specifically has an end portion clamped between thedrive member 54 and sleeve 53 as shown clearly in Fig. 9, and has itsother end aiflxed to the plate 16. This strip 16 functions as a heatbleeder or thermal shunt, to conduct heat away from the drive member 54and, thus, to minimize the effect of heat generated at the cavityresonator during operation of the device, upon the tuning struts. Ittends to hold the temperature uniform over the cavity resonator system,whereby the effect of heatin of the resonator upon the thermal tuninsystem is minimized and the tuning system is quickly responsive tochanges in the potential of the control grid i4.

Electrical connection to the various electrodes of the reflex oscillatorand the thermal tuner element may be established by, in addition to thelead-in. system for the repeller electrode heretofore described, systemsincluding conductors l1 sealed in eyelets 18 on the base l3 by vitreousbeads i9. For reasons which will appear presently, each of the lead-insystems includes a flexible element, such as thin wires 80, in theconnections to the heaters 40 and 73 and grid Hi. The conductors "Hextend to terminal pins carried by an insulating base 8 I, which isprovided with a stem 82 enclosing the metallic exhaust tubulature 88,and is coupled to the base l3 by a metallic mounting ring 84.

An insulating wave guide coupler 85 encompasses the vessel portion l4and is afiixed thereto by a bent-over collar 86. Because of the insulating character of the coupler 85, the enclosing vessel it of thedevice is separated from the external wave guide and, hence, may be at ahigh potential without danger of such potential appearin on the externalwave guide.

It is to be noted that the internal structure may be fabricated from aplurality of subassemblies in which the constituent elements are ac- Icurately positioned in prescribed relation to one another. Theseassemblies are then joined into a unitary mount assembly which is builtaround the plate It as noted heretofore.

The importance of this feature will be appreelated from but briefconsideration of some of the dimensions of important elements in atypical device. In one such device intended for operation at frequenciesof the order of one centimeter, the opening 20 in the plate [6 had aradius of 0.115

" inch and was 0.040 inch deep, the inner diameter of sleeve 53 was 0.10inch and the diameter of grid 29 was 0.046 inch. Obviously, Satisfactoryoperation of a reflex oscillator including elements of these orcomparable dimensions requires that the electrodes of the oscillator bevery accurately aligned. For example, again in a typical structureincluding elements of the dimensions above given, operating requirementsdictated that the opening Zii and grids 25 and 20 be aligned within0.0025 inch.

Meeting of such stringent requirements is facilitated by theconstruction in accordance with features of this invention. The grid 29may be em? ployed as a primary alignment reference in the assembly ofthe device. This grid may be produced, as illustrated in Fig. 6, bywinding the grid wire 29, for example of tungsten, about a molybdenumplate .005 inch thick, the plate having a plurality of circular openings0.046 inch in, diameter. The wire maybe wound 210 turns per,

inch and is brazedrafter winding, to the plate. Grid and support units28, 29 are then punched from the assembly and the'wires ZBare die formedtop'r'ovide a grid of the requisite shape.

The grid-frame assembly 28', 29 is fabricated into a unitary assemblyincluding the ring 26, diaphragm 27, sleeve 53, drive member Mandh'eatbleeder '16 and the grid is then optically aligned axially with theopening 29 and clamped to'an' assembly of the plate 16 and tuner support64 6'5. After" this the grid unit 23, 24, 251s optically aligned axiallywith the grid 29 and clamped in place upon the plate It.

A second subassembly is formed of the wave guide 36, choke joint member32, 33and guide and support E l, 35 and this subassembly is fitted uponthe plate 16, with the wave guide fitted in-the cut-out portion 2i, andclamped in place. The construction thus formed is heated tosimultaneously braze all four of the subassemblies to one another.

The focussing electrode ll and the frame or support 46 therefor areassembled and-after this electrode is optically aligned in accuratecoaxial relation with the grid 29, the frame 46 is welded to the support23 for the grid 25.

The struts 66 and 67 are welded to the collar 56 and the entire assemblythen is mount/scion a fixture. The resonator diaphragm portion 21 isadjusted until the resonator frequency is matched to that of a standard.Then the struts EBand 61 are welded to the support 65 and the assemblyis heat treated to normalize it.

The repeller electrode with the disc 51 and sleeve 52 thereon is mountedby sliding the disc i into the sleeve 53, whereby the r'epeller isaccurately coaxially aligned with the grid 29'. The remaining elementsof the electron gun, assembled as a unit, are then mounted upon theframe 16 by inserting the disc is into the frame and looking it firmlyin place by crimping framedfii over the band or collar 4?, so that thecathode 37, 38

and focussing electrode ll are accurately aligned coaxially with theresonator gap. 7

Finally, the tuner cathode and grid unit, coristituting anothersubassembly, is mounted on the arms 64 and fixed in place by welding theflanges II to the arms as.

When the mount assembly is inserted into the body portion ll] of thevessel, to which theportion I4 hadbe'en joined previously, the fiange35abuts against the flange of the vessel'portion i l. The stem is thensealed to the flange I l, the member's l'l providing sufficientflexibility in the assembly to allow for variations in overall length ofthe mount. The support 34 slides within the vessel portion l4 andautomatically aligns the. wave guide so with the'window i5.

After the base l3 has been sealed to the flange I l, the assembly isheated so that the solder pellets in the recesses is in the coolingblock melt and this block is brazed to the vessel body portion l6 smalldimensions of the elements or therefiex oscillator necessitated by thehigh-operatingfre quencies, high power outputs can be obtained.

Although a specific embodiment of the invention has been shown anddescribed, it willbe understood that it is but illutrative and thatvarious modifications may be made therein without departing from thescope and spirit of" this invention as defined in the appended claims.-

What is claimed is:

1. An electron discharge device comprising an enclosing vessel, aunitary assembly within said vessel, and a cooling block supporting saidassembly from a side wall of said vessel; said=as-- sembly comprising afoundation member afiixed to said block, means including a portion ofsaid member defining a cavity resonator, electronic means for excitingsaid resonator supported from said foundation member and an electronicther mal tuner unit for tuning said resonator supported from saidfoundation member.

2. An electron discharge device comprising an enclosing vessel, aunitary mount within said vessel including a foundation member having anaperture therein, means at opposite ends of said aperture defining acavity resonator with the aperture bounding wall, an electron gunmounted by said member and opposite one end of said aperture, a supportafiixed to said mem b'er resonator mounted by said support, and ametallic block of high heat conductivity afiixed to said member and toan internal wall' of said vessel.

3. An electron discharge device comprising an enclosing vessel, aunitary mount assembly within said vessel including a foundation'platehaving an aperture therein, a flexible diaphragm assembly having a gridportion, extending over one end of said aperture, a grid assemblyextending over the other end of said aperture, havinga grid in alignmentwith said grid portion, and defining a cavity resonator with saiddiaphragm assembly and the bounding wall of said aper ture, anaccelerating grid in alignment with said grid portion, a frame mountingsaid accelerating grid and amxed to said grid assembly, a cathode andauxiliary electrode mounted from said frame and defining an electron gunwith said accelerating grid and an electronic unit for turning saidresonator mounted from said foundation plate,

and means supporting said assembly Within said vessel.

4. An electron discharge device comprising an enclosingvessel having awindow transparent to" electromagnetic wave energy therein, anda'unitary mount assembly Within said vessel and in cluding a foundationplate having an aperture therein and a slot extending from said apertureto one edge of said plate, means mounted bysaid plate and defining acavity resonator with the bounding wall of said aperture, electrodemeans supported from said plate and defining a reflex oscillator withsaid cavity resonator, and a wave guide fitted in said slot, mounted bysaid plate and extending therefrom into immediate prox imity to saidwindow.

5. An electron discharge device comprising an enclosing vessel having abase, a unitary assembly within said vessel comprising a foundationmember having an aperture therein, means mounted by said member anddefining. a cavity' resonator with the bounding Wall of said aper tureand electrode means opposite said aperture; supported from said memberand defining an and an electronic unit for tuning said oscillator unitwith said resonator, flexiblemeans coupling'said assembly to said base,and rigid support means affixed to said assembly and to an inner wallportionof said' vessel removed from said base. j 3 Y T 6. An electrondischarge device comprising an enclosing vessel having a metallic bodyportion, a unitary mount assembly includin a base sealed to one end ofsaid body portion, said assembly including a foundation member, anelectronic unit mounted by said foundation member, flexible meanscoupling said foundation member to said base and a metallic coolingmember amxed to said foundation and having a surface conforming to aninner wall part of said body portion and engaging said wall part, saidcooling member having a recess therein extending from said surface, andbrazing material in said recess, whereby said cooling member may besecurely affixed to said wall part after said assembly is inserted intosaid body portion.

'7. An electron discharge device comprising an enclosing vessel having ametallic body portion, a unitary mount in said body portion andincluding a base sealed to one end of said body portion and a metallicblock having a surface conforming to an inner wall of said body por tionand engaging said wall, said mount comprising also a foundation memberafiixed to said block and having an aperture therein, means mounted bysaid member and defining a cavity resonator with the bounding wall ofsaid aperture, and electrode means supported from said member anddefining an electronic unit with said resonator, means coupling saidblock to said base, said block having a recess therein extending fromsaid surface thereof, and a charge of brazing material in said recess.

8. An electron discharge device comprising an enclosing vessel having aninternal seating surface and a guide portion at one end thereof and abase at the other end thereof, an electronic unit within said vessel,said unit having a portion slidably fitted within said guide portion andhaving a flange bearing against said surface, and flexible meanscoupling said unit to said base.

9. An electron discharge device comprising an enclosing vessel having abase at one end thereof,

a window at the other end thereof and a cylindrical guide portion atsaid other end, an electronic unit within said vessel including a cavityresonator and a wave guide assembly extending from said cavityresonator, said assembly having an end portion slidably fitted withinsaid guide portion, and flexible means coupling said unit to said base.

10. An electron discharge device comprising means defining a cavityresonator having a gap therein and having also a flexible wall portion,an electron gun opposite one end of said gap, a repeller electrodeopposite the other end of said gap, a drive member connected to saidflexible wall portion, a thermal tuner unit coupled to said drive memberfor actuating it, and thermal shunt means connecting said drive memberto said resonator defining means.

11. An electron discharge device comprising a plate having an aperturetherein, means including a flexible member defining a cavity resonatorwith the bounding wall of said aperture, electrode means injuxtaposition to said resonator defining an oscillator unit therewith, adrive member connected to said flexible member, a thermal tuner unitcoupled to said drive member 10 for actuating it, and a member of highheat conductivity connected between said drive member and said plate. a

12. An electron discharge device comprising a metallic plate having anaperture therein, means including a flexible metallic diaphragmextending across one end of said aperture, refining a cavity resonatorwith the bounding wall of said aperture,- a metallic drive membercouple-d to said diaphragm, means in juxtaposition to said resonatordefining, an oscillator unit therewith, a metallic support coupled tosaid plate, a thermal tuner unit mounted by said support and coupled tosaid drive member for actuating it, and a flexible metallic strap havingone end affixed to said plate and its other end fixed to said drivemember at the end thereof adjacent said diaphragm.

13. An electron discharge device comprising a plate having an aperturetherein, means including a flexible member at one end of said aperture,defining a cavity resonator with. the bounding wall of said aperture,electrode means thereadjacent for energizing said resonator, a supportafiixed to said plate and having a pair of outer arms and anintermediate arm, a drive member coupled to said flexible member foractuating it, strut means supported from said intermediate arm andcoupled to said drive member for displacing the latter to flex saidflexible member, thereby to tune said resonator, in accordance withtemperature variations in said strut means, and means for controllablyheating said strut means comprising electrode means mounted from saidpair of arms.

14. An electron discharge device comprising means defining a cavityresonator, said means including a plate having an aperture therein, afirst metallic member having a grid, secured to said plate and extendingacross one end of said aperture and a second metallic member having agrid, aflixed to said plate and extending across the other end of saidaperture, an electron gun opposite said second member, a sleeve memberafiixed to and extending from said first metallic member, a repellerelectrode within said sleeve member, and means locating said repellerelectrode within said sleeve member.

15. An electron discharge device comprising means defining a cavityresonator, said means including a plate having an opening extendingbetween opposite faces thereof, a first member afiixed to one face ofsaid plate, extending across one end of said opening and having a gridportion axially aligned with said opening and a second member affixed tothe opposite face of said plate, extending across the other end of saidopening and having a grid portion axially aligned with said first gridportion, a cylindrical sleeve extending from said first member andaxially aligned with said first grid portion, a repeller electrodewithin said sleeve, a disc fitted within said sleeve and positioningsaid repeller electrode in coaxial relation with said first gridportion,

and an electron gun opposite said second grid portion.

16. An electron discharge device in accordance with claim 15 comprisinga support mounted from said opposite face of said plate and having acylindrical portion coaxial With said second grid portion and whereinsaid gun includes a cathode having an emissive face opposite said secondgrid portion, and an auxiliary electrode coaxial with said emissiveface, the device comprising-"also an annular member fitted; coaxiallyNumber: 1 Within saidcylindricaL partionhandhmounting 2,078,371 saidcathode and said auxiliary electrodeaz-a, 2,412,824; STURE51O.-EKSTRAND: 2,414,785 1 CHARLES :MAGGS: 5 2,416,714 VICTOR L.- RONGL2,4l9,121-- 2,421,273 REFERENCES CITED.

The following references areof record 'in the file'of-this patenitr gUNITED STATES PATENTS 318,706 Number. Name- Date 5 1,474,293 Reynolds:-7 Nov. 13,1923

NflJ-YIQ? Dame 1 .Apr. 27-; 1937 McArthurz: Dec. 17,1946 Harrison.e1;a1; Jan. 21.. 1947 Pierce Mai-1., 4,1947 Clifford (Apr.-15'. 1947Lafierty May 27,1947

FOREIGN @ATENTS Country i- Date Great Britain Juna19, 1922 Germany VFeb. 7, 1920

